Playing midi files with MusicPlayer & Music Sequence - ios

Question

I've successfully gotten iOS to play a .mid (midi) file with a soundfont sample using the following code:
-(void) playMusic:(NSString*) name
{
NSString *presetURLPath = [[NSBundle mainBundle] pathForResource:#"GortsMiniPianoJ1" ofType:#"SF2"];
NSURL * presetURL = [NSURL fileURLWithPath:presetURLPath];
[self loadFromDLSOrSoundFont: (NSURL *)presetURL withPatch: (int)3];
NSString *midiFilePath = [[NSBundle mainBundle] pathForResource:name ofType:#"mid"];
NSURL * midiFileURL = [NSURL fileURLWithPath:midiFilePath];
NewMusicPlayer(&musicPlayer);
if (NewMusicSequence(&musicSequence) != noErr)
{
[NSException raise:#"play" format:#"Can't create MusicSequence"];
}
if(MusicSequenceFileLoad(musicSequence, (CFURLRef)midiFileURL, 0, 0 != noErr))
{
[NSException raise:#"play" format:#"Can't load MusicSequence"];
}
MusicPlayerSetSequence(musicPlayer, musicSequence);
MusicSequenceSetAUGraph(musicSequence, _processingGraph);
MusicPlayerPreroll(musicPlayer);
MusicPlayerStart(musicPlayer);
}
However, the problem comes when I then try to play a second file when the first is still playing.
I've tried many variations. Firstly, the above code will play both tracks simultaneously. Or, I've tried:
DisposeMusicPlayer(musicPlayer);
DisposeMusicSequence(musicSequence);
Before the NewMusicPlayer(&musicPlayer), but this produces a weird version of the tune with only sporadic notes being played.
I'd love to simply call this method, and the next track to be played.

Answer 1

Ok, I found the answer on how to properly dispose of a MusicPlayer and MusicSequence.
-(void) stop
{
OSStatus result = noErr;
result = MusicPlayerStop(musicPlayer);
UInt32 trackCount;
MusicSequenceGetTrackCount(musicSequence, &trackCount);
MusicTrack track;
for(int i=0;i<trackCount;i++)
{
MusicSequenceGetIndTrack (musicSequence, i, &track);
result = MusicSequenceDisposeTrack(musicSequence, track);
}
result = DisposeMusicPlayer(musicPlayer);
result = DisposeMusicSequence(musicSequence);
result = DisposeAUGraph(_processingGraph);
}